1. Field of the Invention
The present invention generally relates to detecting fuel contamination in lubricating oil. More specifically, the present invention relates to in-situ fuel contamination detection to prevent catastrophic failure of engine or other moving parts.
2. Description of the Related Art
Fuel contamination in crankcase oil decreases the lubricating ability of oil and will lead to engine failure. If a fuel injector becomes stuck in the open position, the introduction of large amounts of fuel in crankcase oil will decrease the viscosity of the oil. If the fuel contamination goes undetected, the decrease in viscosity will cause a loss of hydrodynamic lubrication resulting in metal to metal contact and ultimately causing spun and/or seized bearings.
Current methods for fuel detection include absorption spectroscopy, viscosity, and the use of a ‘sniffer’ to measure the aromatics in the gas above the oil. Fuel contamination can be detected using absorbance spectroscopy, but the method has been developed for bench top measurements after a sample of oil has been removed from the crankcase. The difficulties in applying absorbance spectroscopy to an in-situ device are significant and make this particular detection technique impractical. Alternatively, and in the absence of other contaminants in the oil or chemical changes to the oil, fuel (in large enough quantities) can be detected by measuring the viscosity of the oil by comparing to the original oil viscosity. However, oil wear, water contamination, and soot contamination all cause an increase the viscosity of the oil making the detection of fuel contamination in oil by measuring its viscosity difficult. A sniffer requires constant calibration with a known fuel/oil mixture which is impractical in an in-situ device. Still further, fuel does not significantly change other measurable qualities of the oil (conductivity, dielectric constant, resistance, capacitance, polarity, TAN, TBN etc) so a direct in-situ electrical or chemical measurement of the oil to detect the presence of fuel is difficult.
An in-situ fuel contamination detection sensor is needed for early detection of fuel contamination in order to prevent catastrophic failure.